WO2022133963A1

WO2022133963A1 - Battery module, battery pack, electronic apparatus, and battery module manufacturing method and manufacturing device

Info

Publication number: WO2022133963A1
Application number: PCT/CN2020/139184
Authority: WO
Inventors: 刘倩; 梁成都; 叶永煌; 金海族
Original assignee: 宁德时代新能源科技股份有限公司
Priority date: 2020-12-24
Filing date: 2020-12-24
Publication date: 2022-06-30
Also published as: CN114982035A; US20220399607A1; EP4047711A1; EP4047711A4

Abstract

The present application relates to a battery module, the battery module comprising at least first type cells and second type cells connected in series, the first type cells and the second type cells being cells of different chemical systems, the first type cells comprising N first cells, and the second type cells comprising M second cells, N and M being positive integers; when the battery state of health SOH of the first cells is the same as the SOH of the second cells and the state of charge SOC of the first cells is the same as the SOC of the second cells, the ratio of the total charging capacity of a first negative electrode plate of the first cells to the total charging capacity of a second negative electrode plate of the second cells is 0.8-1.2.

Description

Battery pack, battery pack, electrical device, and manufacturing method and manufacturing apparatus of the battery pack

technical field

The present application relates to the technical field of energy storage devices, and in particular, to a battery pack, a battery pack, an electrical device, a method for manufacturing a battery pack, and a manufacturing device for a battery pack.

Background technique

Secondary batteries have the advantages of small size, high energy density, high power density, many cycles of use and long storage time, and are widely used in some electronic equipment, electric vehicles, electric toys and electric equipment, such as mobile phones, notebook computers, Battery cars, electric cars, electric planes, electric ships, electric toy cars, electric toy ships, electric toy planes and electric tools, etc. Secondary batteries are used as power drive power sources for new energy vehicles or large-capacity storage units in energy storage power stations. Usually, multiple single cells need to be connected in series or in parallel to obtain battery packs and battery packs with higher volumetric energy density.

In order to improve the safety of secondary batteries after grouping, a technical solution is proposed to connect a plurality of single cells of different chemical systems in series and/or parallel to form a battery group, wherein a type of cell, for example, has a high energy density ternary batteries containing lithium nickel cobalt manganate lithium metal oxide, another type of batteries such as lithium iron phosphate batteries with high safety. However, for single cells with different chemical systems, the capacity decay characteristics and the charge-discharge characteristics of the cycle process are significantly different. The long-term cycle performance of the battery pack is often limited by the single cells with worse cycle performance, which makes it difficult for some cells in the battery pack to give full play to their electrical performance advantages.

Therefore, how to match the single cells of different chemical systems in the battery pack to realize the long-term cycle performance of the battery pack is an urgent technical problem in the field of secondary batteries.

SUMMARY OF THE INVENTION

For the key technology of hybrid series cells, the prior art only stays at the conceptual level, and there is no specific implementation description for how to match cells of different chemical systems. In particular, in the prior art, there is no record or disclosure about the capacity characteristics, cycle life and other indicators of a battery pack formed by mixing multiple cells in series.

The present application is made in view of the above-mentioned problems in the prior art, and its purpose is to provide a battery pack, by matching the total charging capacity of the negative pole pieces of the cells of different chemical systems, to The capacity design of the chemical system cells is optimized to achieve a long cycle life of the hybrid series module.

A first aspect of the present application provides a battery pack including at least first type cells and second type cells connected in series, wherein the first type cells and the second type cells are of different chemistries System batteries, the first type of batteries includes N first batteries, the second type of batteries includes M second batteries, and N and M are positive integers; When the state of health SOH is the same as the SOH of the second cell, and the state of charge SOC of the first cell is the same as the SOC of the second cell, the first negative electrode of the first cell is The ratio of the total charging capacity of the pole piece to the total charging capacity of the second negative pole piece of the second cell is 0.8 to 1.2.

Optionally, the SOH of the battery state of health of the first cell is the same as the SOH of the second cell, and the state of charge SOC of the first cell is the same as the SOC of the second cell In this case, the ratio of the total charging capacity of the first negative pole piece to the total charging capacity of the second negative pole piece is 0.9 to 1.1.

Optionally, the ratio of the discharge capacity of the first negative pole piece to the discharge capacity of the second negative pole piece is 0.8 to 1.2. Optionally, the ratio of the discharge capacity of the first negative pole piece to the discharge capacity of the second negative pole piece is 0.9 to 1.1.

Optionally, the ratio of the rated capacity of the first type of batteries to the rated capacity of the second type of batteries is 0.8 to 1.2, optionally 0.9 to 1.1.

Optionally, the first negative pole piece and the second negative pole piece also satisfy at least one of the following conditions: (1) the compaction density of the first negative pole piece and the density of the second negative pole piece; The ratio of the compaction density is 0.85 to 1.15, optionally 0.95 to 1.05; (2) the ratio of the coating mass per unit area of the first negative pole piece to the coating mass per unit area of the second negative pole piece is 0.85 to 1.15, optionally 0.95 to 1.05; (3) the ratio of the porosity of the first negative pole piece to the porosity of the second negative pole piece is 0.8 to 1.25, optionally 0.9 to 1.1.

Optionally, the density of the first negative pole piece and the density of the second negative pole piece are independently 1.0 g/cm ³ to 1.9 g/cm ³ , optionally 1.2 g/cm ³ to 1.8 g/cm ³ .

Optionally, the coating mass per unit area of the first negative pole piece and the coating mass per unit area of the second negative pole piece are independently 6 mg/cm ² to 17 mg/cm ² , optionally 8 mg /cm ² to 14 mg/cm ² .

Optionally, the porosity of the first negative pole piece and the porosity of the second negative pole piece are each independently 15% to 35%, optionally 20% to 30%.

Optionally, the negative active material of the first negative pole piece and the negative active material of the second negative pole piece can be independently selected from artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials. One or more of materials and lithium titanate; optionally, the negative active material of the first negative electrode and the negative active material of the second negative electrode have the same composition.

Optionally, the ratio of the number of the first type of batteries to the number of the second type of batteries is 0.1 to 50, optionally 2 to 10.

A second aspect of the present application provides a battery pack, including the battery pack described in the first aspect.

A third aspect of the present application provides an electrical device, comprising the battery pack according to the first aspect or the battery pack according to the second aspect, and using the battery pack or the battery pack as the electrical device power supply or energy storage unit.

A fourth aspect of the present application provides a method for manufacturing a battery pack, comprising the steps of: obtaining a first-type battery cell and a second-type battery cell, wherein the first-type battery cell and the second-type battery cell are of different chemical systems batteries, the first type of batteries includes N first batteries, the second type of batteries includes M second batteries, and N and M are positive integers; When the state SOH is the same as the SOH of the second cell, and the state of charge SOC of the first cell is the same as the SOC of the second cell, the first negative electrode of the first cell is The ratio of the total charging capacity of the sheet to the total charging capacity of the second negative pole piece of the second cell is 0.8 to 1.2; the first type of cell and the second type of cell are electrically connected in a manner including a series connection , to form the battery pack described in the first aspect.

A fifth aspect of the present application provides a battery pack manufacturing equipment, including: a clamping arm unit, the clamping arm unit is used to obtain a first type of battery cell and a second type of battery cell, the first type of battery cell The cells of the second type are cells of different chemical systems, the cells of the first type include N first cells, the cells of the second type include M second cells, and N and M are positive integers ; in the case that the state of health SOH of the first cell is the same as the SOH of the second cell, and the state of charge SOC of the first cell is the same as the SOC of the second cell, The ratio of the total charging capacity of the first negative pole piece of the first battery cell to the total charging capacity of the second negative pole piece of the second battery cell is 0.8 to 1.2; the assembling unit is used to combine the The first type of battery cell and the second type of battery cell are electrically connected in a manner including series connection to form the battery pack described in the first aspect above; and a control unit for controlling the clip arm unit and the assembly unit.

[Technical effect]

In this application, a battery pack includes at least a first type of battery cell and a second type of battery cell with different chemical systems connected in series. The total charging capacity of the battery is set within a specific range to ensure that the life decay rates of cells of different chemical systems are as close as possible during long-term use, thereby avoiding the short life of certain types of cells in the hybrid series module, and significantly improving the model. The overall cycle life of the group.

Since the battery pack and the electrical device in the present application include the battery pack, they have at least the same technical advantages as the battery pack.

Description of drawings

FIG. 1 is a schematic diagram showing one example of a cell of the present application.

FIG. 2 is an exploded view showing one example of the cell of the present application shown in FIG. 1 .

FIG. 3 is a schematic diagram showing one example of the battery pack of the present application.

FIG. 4 is a schematic diagram showing one example of the battery pack of the present application.

FIG. 5 is an exploded view showing one example of the battery pack of the present application shown in FIG. 4 .

FIG. 6 is a schematic diagram showing an example of an electrical device using the battery pack of the present application as a power source.

Label description

5, 5a, 5b cells

51 shell

52 Electrode assembly

53 Cover

4 battery packs

1 battery pack

2 upper cabinet

3 lower cabinets

Detailed ways

A "range" disclosed herein is defined in the form of a lower limit and an upper limit, a given range being defined by the selection of a lower limit and an upper limit, the selected lower limit and the upper limit defining the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive, and may be arbitrarily combined, ie, any lower limit may be combined with any upper limit to form a range. For example, if the ranges of 60-120 and 80-110 are listed for a particular parameter, it is to be understood that the ranges of 60-110 and 80-120 are also contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the

maximum range values

3, 4, and 5 are listed, the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5. In this application, unless stated otherwise, the numerical range "a-b" represents an abbreviated representation of any combination of real numbers between a and b, where both a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed in the text, and "0-5" is just an abbreviated representation of the combination of these numerical values. In addition, when a parameter is expressed as an integer greater than or equal to 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and the like.

In this application, unless otherwise specified, all the embodiments and preferred embodiments mentioned herein can be combined with each other to form new technical solutions.

In this application, unless otherwise specified, all the technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

In this application, if there is no special instruction, all the steps mentioned herein can be performed sequentially or randomly, but are preferably performed sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed in sequence, and may also include steps (b) and (a) performed in sequence. For example, reference to the method may further include step (c), indicating that step (c) may be added to the method in any order, eg, the method may include steps (a), (b) and (c) , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.

In this application, if there is no special description, the "comprising" and "comprising" mentioned in this document indicate an open type, and can also be a closed type. For example, the terms "comprising" and "comprising" can mean that other components not listed may also be included or included, or only the listed components may be included or included.

In the description herein, it should be noted that, unless otherwise specified, “above” and “below” are inclusive of the numbers, and “several” in “one or more” means two or more.

In the description herein, unless stated otherwise, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied by either of the following: A is true (or present) and B is false (or absent); A is false (or absent) and B is true (or present) ; or both A and B are true (or present).

[Batteries]

In this application, "cell" refers to a battery cell that can be independently charged and discharged. The components of the battery cell may include positive pole pieces, negative pole pieces, separators, electrolytes, and outer packaging for encapsulating the positive pole pieces, negative pole pieces, separators, and electrolytes. The application does not have any special restrictions on the type and shape of the cells, which may be soft-wrapped cells, cylindrical cells, or square cells and other types of cells. The batteries in this application can be lithium-ion batteries, potassium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, etc., and are particularly preferably lithium-ion batteries. During the charging and discharging process of the battery, active ions are inserted and extracted back and forth between the positive electrode and the negative electrode. The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.

In this application, the "chemical system" of the battery cell is divided according to the composition of the positive electrode active material used in the positive electrode sheet in the battery cell, and the elements or substances that are doped or coated with the positive electrode active material are not limited. For example, a battery cell whose positive active material is lithium iron phosphate (including doped with Mn or V element) can be defined as a lithium iron phosphate chemical system battery cell. A battery cell whose positive active material is nickel cobalt lithium manganate (generally referred to as NCM) can be defined as a battery cell of an NCM chemical system. Further, the chemical system of the cell can be further limited according to the relative _contents of _nickel , _cobalt , and _manganese in the positive electrode active material. Defined as NCM523 chemical system battery, the positive active material is LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (generally referred to as NCM622) battery can be defined as NCM622 chemical system battery, the positive active material is LiNi _0.8 Co _0.1 Mn _0.1 O ₂ ( Generally referred to as NCM811) cells can be defined as NCM811 chemical system cells. The nickel-cobalt-aluminate lithium system battery (commonly referred to as NCA) as the positive electrode material can be defined as the NCA chemical system battery. In addition, in the present application, a hybrid system cell can also be used, for example, a hybrid system cell including NCM and NCA.

Below, the basic structures of the negative electrode tab, the positive electrode tab, the electrolyte, and the separator included in the battery cell in the present application will be described first.

The battery cell of the present application includes a negative electrode plate, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, and the negative electrode film layer contains a negative electrode active material.

In one embodiment of the present application, the negative electrode active material of the negative electrode film layer may include common negative electrode active materials, for example, natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate one or more of them. The silicon-based material may be selected from one or more of elemental silicon, silicon oxide, and silicon-carbon composite. The tin-based material can be selected from one or more of elemental tin, tin oxide compounds, and tin alloys.

In the battery cell of the present application, the negative electrode film comprises negative electrode active material and optional binder, optional conductive agent and other optional auxiliary agents, and is usually formed by coating and drying the negative electrode slurry. The negative electrode slurry is usually formed by dispersing the negative electrode active material and optional conductive agent and binder in a solvent and stirring uniformly. The solvent can be N-methylpyrrolidone (NMP) or deionized water.

As an example, the conductive agent may include one or more of superconducting carbon, carbon black (eg, acetylene black, ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

As an example, the binder may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA) , one or more of sodium alginate (SA) and carboxymethyl chitosan (CMCS). As an example, the binder may include one of styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS) or several. Other optional auxiliary agents are, for example, thickeners (such as sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials, and the like.

In addition, in the battery cell of the present application, the negative pole piece does not exclude other additional functional layers other than the negative electrode film layer. For example, in certain embodiments, the negative electrode sheet of the present application may further include a conductive primer layer (eg, a conductive agent and a bonding agent) disposed on the surface of the negative electrode current collector sandwiched between the negative electrode current collector and the first negative electrode film layer. composition). In other embodiments, the negative electrode sheet of the present application may further include a protective cover layer covering the surface of the second negative electrode film layer.

In the cell of the present application, the negative electrode current collector may be a metal foil or a composite current collector, for example, the metal foil may be a foil composed of copper foil, silver foil, iron foil, or an alloy of the above metals. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. ) formed on the base layer of polymer materials (such as polypropylene PP, polyethylene terephthalate PET, polybutylene terephthalate PBT, polystyrene PS, polyethylene PE and its copolymers, etc.). formed on the base layer).

In the battery cell of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material. For example, the positive electrode current collector has two opposite surfaces in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector. In the battery cell of the present application, the positive electrode current collector may be a metal foil or a composite current collector, for example, the metal foil may be an aluminum foil, and the composite current collector may include a polymer material base layer and a layer formed on the polymer material. A metal layer on at least one surface of the material base layer. The composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) Glycol ester PET, polybutylene terephthalate PBT, polystyrene PS, polyethylene PE and its copolymers etc.

In the battery cell of the present application, the positive electrode active material can be a known positive electrode active material for battery cells in the art. For example, the positive active material may include one or more of the following: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for battery cells can also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include but are not limited to lithium cobalt oxides (such as LiCoO ₂ ), lithium nickel oxides (such as LiNiO ₂ ), lithium manganese oxides (such as LiMnO ₂ , LiMn ₂ O ₄ ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NCM333), LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (NCM523), LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (NCM211), LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (NCM622), LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811)), lithium nickel cobalt aluminum oxide (such as One or more of LiNi _0.85 Co _0.15 Al _0.05 O ₂ ) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (eg, LiFePO ₄ (LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (eg, LiMnPO ₄ ), lithium manganese phosphate and carbon One or more of the composite materials, lithium iron manganese phosphate, lithium iron manganese phosphate and carbon composite materials.

In some embodiments, the positive electrode film layer also optionally includes a binder. Non-limiting examples of binders that can be used in the positive film layer may include one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene tri- Element copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.

In some embodiments, the positive electrode film layer may also optionally contain a conductive agent. Examples of the conductive agent used in the positive electrode film layer may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In one embodiment of the present application, the positive electrode can be prepared by dispersing the above-mentioned components for preparing the positive electrode, such as positive electrode active material, conductive agent, binder and any other components, in a solvent (such as N- Methylpyrrolidone), a uniform positive electrode slurry is formed; the positive electrode slurry is coated on the positive electrode current collector, and the positive electrode sheet can be obtained after drying, cold pressing and other processes.

The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The electrolyte solution includes an electrolyte salt and a solvent. In some embodiments, the electrolyte salt may be selected from lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium perchlorate (LiClO ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), bisfluorosulfonylidene Lithium Amide (LiFSI), Lithium Bistrifluoromethanesulfonimide (LiTFSI), Lithium Trifluoromethanesulfonate (LiTFS), Lithium Difluorooxalate Borate (LiDFOB), Lithium Dioxalate Borate (LiBOB), Lithium Difluorophosphate One or more of (LiPO ₂ F ₂ ), lithium difluorodioxalate phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).

In one embodiment of the present application, the solvent may be selected from one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate ( DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC) ), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and Ethyl sulfone (ESE).

In an embodiment of the present application, based on the total weight of the electrolyte, the content of the solvent is 60-99 wt %, for example, 65-95 wt %, or 70-90 wt %, or 75- 89% by weight, or 80-85% by weight. In an embodiment of the present application, based on the total weight of the electrolyte, the content of the electrolyte is 1-40 wt %, for example 5-35 wt %, or 10-30 wt %, or 11- 25% by weight, or 15-20% by weight.

In one embodiment of the present application, the electrolyte may optionally contain additives. For example, the additives may include one or more of the following: negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performance of the battery, such as additives to improve battery overcharge performance, additives to improve battery high temperature performance, Additives to improve low temperature performance of batteries, etc.

In an embodiment of the present application, the cell further includes a separator, which separates the anode side from the cathode side of the cell, and provides selective permeation or barrier to substances of different types, sizes and charges in the system For example, the separator can insulate the electrons, physically isolate the positive and negative active materials of the cell, prevent the internal short circuit and form an electric field in a certain direction, and at the same time enable the ions in the battery to pass through the separator to move between the positive and negative electrodes. .

In one embodiment of the present application, the material used to prepare the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer can be the same or different.

In one embodiment of the present application, the above-mentioned positive electrode sheet, negative electrode sheet and separator can be made into electrode assemblies/bare cell cores through a winding process or a lamination process.

In one embodiment of the present application, the cell may include an outer package, and the outer package may be used to encapsulate the above-mentioned electrode assembly and electrolyte. In some embodiments, the outer packaging of the cell may be a hard case, such as a hard plastic case, an aluminum case, a steel case, and the like. In other embodiments, the outer package of the battery cell may be a soft package, such as a bag-type soft package. The material of the soft bag may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), and the like.

FIG. 1 is a schematic diagram showing one example of the battery cell 5 of the present application. FIG. 2 is an exploded view showing one example of the battery cell 5 of the present application shown in FIG. 1 .

The outer package may include a casing 51 and a cover plate 53 , the casing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are enclosed to form a receiving cavity. The housing 51 has an opening that communicates with the accommodating cavity, and a cover plate 53 can cover the opening to close the accommodating cavity. The positive pole piece, the negative pole piece and the separator can be rolled or laminated to form the electrode assembly 52 , the electrode assembly is packaged in the accommodating cavity, and the electrolyte is infiltrated in the electrode assembly 52 . The number of electrode assemblies 52 included in the battery cell 5 may be one or more.

[Battery]

In this application, a "battery pack" is formed by electrically connecting a certain number of cells together and putting them into a frame in order to protect the cells from external impact, heat, vibration, etc. The shape of the battery cell of the present application can be cylindrical, square or any other shape.

In the present application, several cells can be assembled together to form a battery pack, and the battery pack contains two or more cells, the specific number of which depends on the application of the battery pack and the parameters of a single battery pack.

FIG. 3 is a schematic diagram showing one example of the battery pack of the present application. 3, in the battery pack 4, a plurality of

cells

5a, 5b may be arranged in sequence along the length direction of the battery pack 4 (5a may be the first cell, 5b may be the second cell). Of course, it can also be arranged in any other manner. Further, the plurality of

battery cells

5a and 5b can be fixed by fasteners. Optionally, the battery pack 4 may further include a housing having an accommodating space, and the plurality of

packs

5a, 5b are accommodated in the accommodating space.

In this application, a battery pack includes at least a first type of battery cell and a second type of battery cell connected in series, the first type of battery cell and the second type of battery cell are cells of different chemical systems, the first type of battery cell The cell includes N cells, the first type of cell includes a first cell; the second type of cell includes M cells, and the second type of cell includes a second cell; N and M is a positive integer; the SOH of the battery state of health of the first cell is the same as the SOH of the second cell, and the state of charge SOC of the first cell is the same as the SOC of the second cell In this case, the ratio of the total charging capacity of the first negative pole piece of the first battery cell to the total charging capacity of the second negative pole piece of the second battery cell is 0.8 to 1.2.

Among them, "SOH" represents the state of health (State of Health), which refers to the ratio of the total capacity of the current cell to the initial total capacity of the cell. For example, it can be 100%, 98%, 95%, 90%, 85%, 80%, 75%, 70%. "SOC" represents the state of charge (State Of Charge), which refers to the ratio of the remaining power of the current cell to the rated capacity under the same conditions, for example, it can be 100%, 99%, 90%, 80%, 70%, 60% %, 50%, 40%, 30%, 20%, 10%, 0%.

It should be understood that, due to the accuracy of the test and the unavoidable test error, the range referred to by "the state of health SOH of the first cell is the same as the SOH of the second cell" in this application refers to the state of health SOH of the first cell The ratio of the absolute value of the difference from the SOH of the second cell to the average value of the two is not more than 5%. Similarly, "the state of charge SOC of the first cell is the same as the SOC of the second cell" refers to the range of the absolute value of the difference between the state of charge SOC of the first cell and the SOC of the second cell and the The ratio of the average value of the two should not exceed 5%.

(About SOH test)

In this application, the SOH of the first cell and the SOH of the second cell can be obtained by testing methods known in the art. As an example, the following methods can be used to test:

Refer to GB/T 31484-2015 "Cycle Life Requirements and Test Methods of Power Batteries for Electric Vehicles" to test the actual capacity of the cells, and the ratio of the actual capacity measured by the same test process to the rated capacity of the freshly manufactured cells is SOH.

Actual capacity (calculated as: Capx) test steps:

Let the battery to be tested stand for 30 minutes at 25°C; 2) 0.33C (C represents the rated capacity of the battery. Among them, the charge/discharge current is the rate multiplied by the rated capacity of the battery, and the rated capacity is calculated by the battery or the battery. The battery module to which the cell belongs or the capacity of the battery cell identified in the GBT certification document of the battery pack to which the cell belongs shall prevail) Constant current discharge to the discharge termination voltage of the battery cell, and then stand for 30 minutes; 3) 0.33C constant current charging To the cell charging termination voltage, constant voltage charge to the current <0.05C, let stand for 5 minutes; 4) 0.33C constant current discharge to the cell discharge termination voltage, then let stand for 5 minutes. The discharge capacity measured from step 3) to step 4) is recorded as Capx.

The percentage of Capx to the rated capacity C is the SOH.

(About SOC test)

In this application, the SOC of the first battery cell and the SOC of the second battery cell can be obtained by testing methods known in the art. As an example, the following methods can be used to test:

Refer to GB/T 31484-2015 "Cycle Life Requirements and Test Methods of Power Batteries for Electric Vehicles" to test the capacity that the cells can release under the same discharge conditions as the rated capacity test process, the discharge capacity is recorded as Capy, and the capacity accounts for The percentage of the actual capacity Capx of the cell is the SOC.

In the present application, adjusting the SOH of the first cell and the SOH of the second cell to the same method can be performed by using a method known in the art. As an example, the following methods can be used to adjust:

If the SOH of a certain cell is lower, the SOH of that cell can be adjusted as the target SOH of the higher SOH cell. For the adjustment method, refer to the cycle life test method in GB/T 31484-2015 "Cycle Life Requirements and Test Methods of Power Batteries for Electric Vehicles" until the percentage of the actual capacity of the cells to the rated capacity reaches the target value.

The cycle life test process is as follows:

1) Let the cell to be tested stand for 30 minutes at 25°C; 2) Discharge the cell with a constant current of 0.33C to the discharge termination voltage of the cell, and then let it stand for 30 minutes; 3) Charge it with a constant current of 0.33C to the termination voltage of the cell, Constant voltage charge to current <0.05C, let stand for 5 minutes; 4) 0.33C constant current discharge to cell discharge termination voltage, then let stand for 5 minutes.

Steps 3) to 4) are one charge-discharge cycle for the battery cell.

Repeat the above steps 3) to 4) n times until the discharge capacity of the nth time Capn=target SOH*rated capacity.

In the present application, the method of adjusting the SOC of the first battery cell and the SOC of the second battery cell to be the same can be performed by using a method known in the art. As an example, the following methods can be used to adjust:

The method of adjusting SOC is as follows:

1) Set the target SOC, such as 0% SOC; 2) Let the cell to be tested stand at 25°C for 30 minutes; 3) Discharge the cell with a constant current of 0.33C to the discharge termination voltage of the cell, and then let it stand for 30 minutes. That is, 0% SOC is reached. If the target SOC is x%SOC, the steps to adjust the SOC process are as follows: 1) Let the cell to be tested stand at 25°C for 30 minutes; 2) 0.33C constant current discharge to the cell discharge termination voltage, and then stand for 30 minutes ; 3) 0.33C constant current charge to the cell charging termination voltage, constant voltage charging to the current <0.05C, let stand for 5 minutes; 4) 0.33C constant current discharge to the cell discharge termination voltage, then stand for 5 minutes. The discharge capacity measured from step 3) to step 4) is recorded as Capx; 5) 0.33C constant current charge to the cell charging termination voltage, constant voltage charge to current < 0.05C, let stand for 5 minutes; 6) 0.33C constant current The current was discharged to remaining capacity=x%SOC*Capx, and then left to stand for 5 minutes.

(About the test of the total charging capacity of the negative pole piece)

In this application, the total charging capacity of the negative electrode sheet refers to the amount of lithium ions that the negative electrode electrode sheet can accept, and the unit is mAh or Ah. The total charging capacity of the negative pole piece of the first battery cell and the total charging capacity of the negative pole piece of the second battery cell can be obtained by testing methods known in the art. As an example, the following methods can be used to test:

(1) The sampling requirements of the pole piece are as follows:

Take the negative pole piece that has been coated on one side and has been cold-pressed (if it is a pole piece coated on both sides, you can wipe off the negative film layer on one side first), or the negative pole piece that is disassembled from the cell ( Let the cell stand at 25°C for 30 minutes; discharge it with a constant current of 0.33C to the discharge termination voltage of the cell, then let it stand for 30 minutes for full discharge, then disassemble the cell and take out the negative pole piece, if it is double-sided coating For the pole piece, first wipe off the negative film layer on one side, rinse with DMC solution properly, and dry it for later use). Use a ruler to measure the length and width of the negative pole piece, and the area of the negative pole piece is equal to the product of the length and width. The sampling position of the negative pole piece is: select any position in the middle of the edge > 15mm;

(2) the negative pole piece is provided with one side of the negative electrode film layer and the lithium piece as the counter electrode, and the coin cell half-cell is assembled;

(3) The charging capacity of the negative pole piece per unit area and the total charging capacity of the negative pole piece:

The test voltage is 0.05-2.0V, the test temperature is 25°C, the charge/discharge rate is 0.1C, and no less than 10 parallel samples are taken. The charging capacity of the negative pole piece under the area; the charging capacity of the negative pole piece obtained by the above test is divided by the area of the negative pole piece, that is, the charging capacity of the negative pole piece per unit area can be obtained;

The total charging capacity of the negative pole piece = the charging capacity of the negative pole piece per unit area × the total area of the negative pole piece in the battery cell. It is the sum of the area of the negative electrode film layer participating in the charge-discharge reaction on the upper and lower surfaces of the negative electrode pole piece (usually, the area of the negative electrode film film participating in the charge-discharge reaction in the secondary battery is equal to the total area of the positive electrode film region).

In this application, for example, in the case where the first type of battery and the second type of battery are both lithium-ion batteries, the first type of battery and the second type of battery are in the same SOH and SOC state, the said When the ratio of the total charging capacity of the first negative pole piece of the first battery cell to the total charging capacity of the second negative pole piece of the second battery cell is within the above range, the first type of battery cell and the The negative pole pieces of the second type of cells have the same ability to intercalate lithium ions (the amount of lithium ions that can be intercalated), so that the life decay rates of cells of different types of chemical systems during series use are basically the same, thereby significantly improving The overall cycle life of the battery pack.

In some embodiments of the present application, the state of health (SOH) of the first battery cell is the same as the SOH of the second battery cell, and the state of charge (SOC) of the first battery cell is the same as that of the second battery cell. Under the condition that the SOC of the core is the same, the ratio of the total charging capacity of the first negative pole piece to the total charging capacity of the second negative pole piece is 0.9 to 1.1. In the present application, when the ratio of the total charging capacity of the first negative pole piece of the first battery cell to the total charging capacity of the second negative pole piece of the second battery cell is within the above range, the first battery can be further improved. The ability of lithium ions (the amount of lithium ions that can be inserted) of the negative pole pieces of the second-type cell and the second-type cell is consistent, so that the life decay rate of cells of different types of chemical systems can be consistent during series use. , thereby further improving the overall cycle life of the battery pack.

In some embodiments of the present application, the first negative pole piece and the second negative pole piece also satisfy at least one of the following conditions:

(1) the ratio of the compaction density of the first negative pole piece to the compaction density of the second negative pole piece is 0.85 to 1.15, optionally 0.95 to 1.05;

(2) the ratio of the coating mass per unit area of the first negative pole piece to the coating mass per unit area of the second negative pole piece is 0.85 to 1.15, optionally 0.95 to 1.05;

(3) The ratio of the porosity of the first negative pole piece to the porosity of the second negative pole piece is 0.8 to 1.25, optionally 0.9 to 1.1.

In the present application, the compaction density of the negative electrode sheet refers to the density of the negative electrode film layer on one side surface of the negative electrode current collector. In the present application, when the ratio of the compaction density of the first negative pole piece to the compaction density of the second negative pole piece is further controlled within the above range, it can ensure that the first cell and the second cell have good kinetics And there are fewer side reactions on the surface of the negative electrode, thereby further improving the kinetic performance and cycle life of the battery pack.

In some embodiments of the present application, the compaction density of the first negative pole piece and the compaction density of the second negative pole piece are each independently 1.0 g/cm ³ to 1.9 g/cm ³ . Optionally 1.2 g/cm ³ to 1.8 g/cm ³ .

(About compaction density test)

In the present application, the compaction density of the negative pole piece can be measured by a method known in the art. As an example, the following method can be used for testing: take a negative pole piece coated on one side and cold pressed (if it is a pole piece coated on both sides, you can wipe off the negative film layer on one side first), or from The negative pole piece disassembled from the cell (the negative pole piece disassembled from the cell can be simply rinsed with DMC to remove the residual electrolyte or reaction by-products on the surface and inside of the pole piece), and the area is punched to The small disc of S1 is weighed and recorded as M1; the thickness of the negative film layer is measured, recorded as H; then the negative film layer is wiped off, and the weight of the negative current collector is weighed, recorded as M2; the pressure of the negative film layer is recorded as M2; Solid density dc=(M1-M2)/S1/H.

In this application, the coating mass per unit area of the negative electrode sheet refers to the mass of the negative electrode film layer provided on the surface of one side of the negative electrode current collector per unit area. In the present application, when the ratio of the coating mass per unit area of the first negative pole piece to the coating mass per unit area of the second negative pole piece is further controlled to be within the above range, since the amount of the negative electrode graphite is equivalent, the amount of lithium ions that can be embedded will be reduced. The number of active sites is the same, the consumption rate of lithium ion film formation and the loss rate of active material are similar, and the aging rate of the battery cell is relatively close, so the consistency of the overall performance of the battery pack can be further improved.

In some embodiments of the present application, the coating mass per unit area of the first negative pole piece and the coating mass per unit area of the second negative pole piece are each independently 6 mg/cm ² to 17 mg/cm ² . Optionally 8 mg/cm ² to 14 mg/cm ² .

(About the test of the coating quality per unit area of the negative pole piece)

In this application, the coating quality per unit area of the negative pole piece can be measured by a method known in the art. As an example, the following methods can be used to test:

Let the cell stand at 25°C for 30 minutes; discharge it with a constant current of 0.33C to the discharge termination voltage of the cell, then let it stand for 30 minutes for full discharge, then disassemble the cell, and take the negative pole piece to be tested (if it is double-sided). For the coated negative pole piece, the active material layer on one side can be wiped off first), cut into small discs with an area of S1, weigh the small discs, and record their mass as M1; In deionized water, the negative electrode active material layer and the negative electrode current collector are completely peeled off, and the mass of the negative electrode current collector is weighed and recorded as M2; thus, the coating quality per unit area of the negative electrode pole piece can be calculated according to the formula: Coating mass per unit area=(M1-M2)/S1.

In the present application, the porosity of the negative electrode sheet refers to the ratio of the void volume to the total volume of the negative electrode electrode sheet in the negative electrode electrode sheet with the negative electrode film layer on both the upper and lower surfaces of the negative electrode current collector. In the present application, when the ratio of the porosity of the first negative pole piece to the porosity of the second negative pole piece is further controlled to be within the above range, since the kinetic performance of the negative pole piece is equivalent and the degree of side reactions is equivalent, the electrical The charging, rate and power performance between the cores are consistent, and at the same time, a better life performance matching can be achieved.

In some embodiments of the present application, the porosity of the first negative pole piece and the porosity of the second negative pole piece are each independently 15% to 35%. Optionally 20% to 30%.

(About porosity test)

In this application, the porosity of the negative pole piece refers to the ratio of the pore volume in the pole piece to the total volume, which can be obtained by testing by methods known in the art. As an example, the following method can be used to conduct the test: for example, the AccuPyc II 1340 automatic true density tester of Micromeritics Company of the United States is used, and the test is carried out with reference to the national standard GB/T 24586-2009.

The specific test steps are as follows: let the cell stand at 25°C for 30 minutes; discharge it with a constant current of 0.33C to the discharge termination voltage of the cell, and then let it stand for 30 minutes; then disassemble the cell and take out the negative pole piece; soak in DMC The pole piece is 20 hours, and the DMC is replaced once during this period, and the drying room is dried for > 2 hours until it is completely dry; punch > 30 small rounds with a diameter of 14mm with a punching machine. , at least 1 time per piece, take the average value, package in ziplock bag, and mark the thickness; use the inert gas (helium) replacement method with small molecular diameter, combined with Archimedes' principle and Bohr's law, to accurately measure the real volume of the tested material ; Porosity P=(V2-V1)/V2*100%, apparent volume V2=S*H*A, where: S-area, cm ² ; H-thickness, cm; A-number of samples, EA; V1-true volume of the sample, cm ³ , obtained by testing; V2-apparent volume of the sample, cm ³ .

In some embodiments of the present application, the negative active material of the first negative electrode and the negative active material of the second negative electrode can be independently selected from artificial graphite, natural graphite, soft carbon, hard carbon, silicon One or more of base materials, tin-based materials, and lithium titanate. Optionally, the negative active material of the first negative electrode and the negative active material of the second negative electrode have the same gram capacity. In this application, when the negative electrode active material of the first negative electrode and the negative active material of the second negative electrode have the same composition, the negative electrodes of the first type of battery cell and the second type of battery cell can be better The ability of the chip to intercalate lithium ions (the amount of lithium ions that can be intercalated) is consistent, so that the life decay rates of cells of different types of chemical systems during series use are basically the same, thereby significantly improving the overall cycle life of the battery pack.

In some embodiments of the present application, the ratio of the rated capacity of the first type of cells to the rated capacity of the second type of cells is 0.8 to 1.2. Optionally 0.9 to 1.1. In this application, on the basis of controlling the relationship between the total charging capacity of the first negative pole piece and the second negative pole piece, when the rated capacity of the first cell and the second cell is further controlled to be within the above range, due to the mixed series mode The consistency of the cell capacity in the group is good, and the capacity of the module is not affected by the short board of the capacity of a single cell, so the energy throughput of the module can be improved.

In this application, the rated capacity of the first cell and the rated capacity of the second cell can be obtained by testing methods known in the art, or the cell, or the battery module to which the cell belongs, or the battery to which the cell belongs. The capacity of the battery cells identified in the GBT certification document of the package shall prevail.

In some embodiments of the present application, the ratio of the number of the first type of cells to the number of the second type of cells is 0.1 to 50, optionally 1 to 30.

In the battery pack of the present application, the first type of battery cells and the second type of battery cells are electrically connected, so as to output electric energy externally or store electric energy with required voltage and current. Wherein, the first type of battery cells and the second type of battery cells may be electrically connected in series or in a series/parallel combination. In the present application, after the first type of battery cell and the second type of battery cell are electrically connected at least in series, the first type of battery cell and the second type of battery cell can be charged/discharged synchronously, which facilitates the realization of different types of batteries in the battery pack. The capacity fading characteristics of the cells in the chemical system remain consistent, which is conducive to achieving a long cycle life of the battery pack. In a specific example, the first type of battery cell and the second type of battery cell are electrically connected in series.

In some embodiments of the present application, the electrical connection manner of the first type of cells and the second type of cells further includes parallel connection. In this application, the parallel connection of the first type of batteries and the second type of batteries may be that a plurality of first type of batteries and the second type of batteries are connected in series to form sub-modules, and then on this basis, the same Two or more sub-modules of the total voltage are connected in parallel. This can further improve the external output current of the battery pack.

[Manufacturing method]

Another aspect of the present application provides a method for manufacturing a battery pack, which includes the steps of: obtaining a first type of battery cell and a second type of battery cell, wherein the first type of battery cell and the second type of battery cell are of different chemical systems batteries, the first type of batteries includes N first batteries, the second type of batteries includes M second batteries, and N and M are positive integers; When the state SOH is the same as the SOH of the second cell, and the state of charge SOC of the first cell is the same as the SOC of the second cell, the first negative electrode of the first cell is The ratio of the total charging capacity of the sheet to the total charging capacity of the second negative pole piece of the second cell is 0.8 to 1.2; the first type of cell and the second type of cell are electrically connected in a manner including a series connection , to form the battery pack as described above.

The battery pack using the manufacturing method of the present application can ensure that the life decay rates of cells of different chemical systems during long-term use are as close as possible, thereby avoiding the short life of certain types of cells in the hybrid series module, and significantly improving the module. the overall cycle life.

The technical features of the battery pack in the present application are also applicable to the manufacturing method of the battery pack, and produce corresponding beneficial effects.

Both the first type of cells and the second type of cells can be obtained commercially or prepared by methods known in the art. As an example, the positive pole piece, the separator and the negative pole piece can be formed by a stacking process or a winding process to form a battery cell; the battery cell is put into an outer package, injected with an electrolyte, and after encapsulation and other subsequent processes, a battery is obtained. monomer.

The positive electrode sheet can be prepared according to conventional methods in the art. For example, the positive electrode active material, the conductive agent and the binder are dispersed in a solvent to form a uniform positive electrode slurry, such as N-methylpyrrolidone (NMP); the positive electrode slurry is coated on the positive electrode current collector, and the After drying, cold pressing and other processes, a positive electrode sheet is obtained.

The negative pole piece can be prepared according to conventional methods in the art. For example, the negative electrode active material, conductive agent, binder and thickener are dispersed in a solvent to form a uniform negative electrode slurry, the solvent is deionized water, for example; the negative electrode slurry is coated on the negative electrode current collector, and dried After drying, cold pressing and other processes, a negative electrode piece is obtained.

[Manufacturing Equipment]

Another aspect of the present application provides a manufacturing equipment for a battery pack, including: a clamping arm unit, the clamping arm unit is used to obtain a first type of battery cell and a second type of battery cell, the first type of battery cell and the second type of battery cell. Class cells are cells of different chemical systems, the first type of cells includes N first cells, the second type of cells includes M second cells, and N and M are positive integers; When the state of health SOH of the first cell is the same as the SOH of the second cell, and the state of charge SOC of the first cell is the same as the SOC of the second cell, the first cell The ratio of the total charging capacity of the first negative pole piece of a cell to the total charging capacity of the second negative pole piece of the second cell is 0.8 to 1.2; A type of battery cell and the second type of battery cell are electrically connected in a manner including series connection to form a battery pack as described above; and a control unit for controlling the clamping arm unit and the assembling unit .

[battery pack]

Another aspect of the present application also provides a battery pack, which includes any one or several battery packs of the present application. The number of battery packs contained in the battery pack can be adjusted according to the application and capacity of the battery pack. Optionally, the battery pack may further include auxiliary components such as a battery management system module (BMS) and cooling/heating components.

In some embodiments, the battery pack includes more than two battery packs, each battery pack being a battery pack as described herein. The battery pack has high safety, and at the same time, the capacity decay trend of the cells of different chemical systems is basically the same, so its cycle life can be significantly improved.

6 and 7 are the battery pack 1 as an example. 6 and 7 , the battery pack 1 may include a battery case and a plurality of battery packs 4 provided in the battery case. The battery box includes an upper box body 2 and a lower box body 3 . The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery pack 4 . The plurality of battery packs 4 can be arranged in the battery case in any manner.

[electricity device]

Another aspect of the present application further provides an electrical device comprising the battery pack or battery pack described in the present application. The battery pack or battery pack can be used as a power source for an electrical device to provide power to the electrical device; it can also be used as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, mobile devices (such as mobile phones, laptop computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric vehicles, etc.) Golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc. The electrical device may select an electrochemical device, such as a battery pack or a battery pack, according to its usage requirements.

FIG. 8 is an electrical device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. The electrical device can use a battery pack or a battery module.

Example

Hereinafter, the technical solutions and advantages of the present application will be described in detail through specific embodiments.

"Cell Preparation"

Referring to GB/T 31484-2015 "Cycle Life Requirements and Test Methods of Power Batteries for Electric Vehicles", the preparation methods of the cells in each embodiment and comparative example are as follows.

1. Preparation of positive electrode slurry

The positive electrode material, the conductive carbon Super P, and the binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in an appropriate amount of N-methylpyrrolidone (abbreviated as NMP) solvent at a weight ratio of 95:3:2 to form a Uniform and stable slurry with a viscosity of 10000mPa·s, the slurry does not gel, stratify or settle within 24 hours of standing.

2. Preparation of positive electrode pieces

The positive electrode material slurry is uniformly coated on the Al foil of the positive electrode current collector, and after drying, the polar piece is cold-pressed to a design compaction, and divided into strips for use to obtain a positive electrode polar piece.

3. Preparation of electrolyte

An equal volume of ethylene carbonate was dissolved in propylene carbonate, and then the lithium hexafluorophosphate was uniformly dissolved in the mixed solvent (the lithium hexafluorophosphate concentration was 1.0 M/L) for subsequent use to obtain an electrolyte solution.

4. Preparation of negative pole pieces

Negative active materials such as graphite and conductive carbon, binder polystyrene butadiene copolymer (SBR), thickener sodium carboxymethyl cellulose (CMC) in an appropriate weight ratio of 95:2:2:1. Fully stir and mix in water solvent to form a uniform negative electrode stable slurry; this slurry is evenly coated on the negative electrode current collector Cu foil, and after drying, the pole piece is cold pressed to the design compaction, and divided into strips for use.

5. Isolation film

Choose PE as the isolation film.

6. Preparation of cells

Using the conventional cell manufacturing process, the positive electrode, separator and negative electrode are wound together to form a bare cell, then placed in the battery case, injected with electrolyte, followed by chemical formation, sealing and other processes, and finally obtained Rechargeable power cells.

"Assembly of the battery pack"

The battery pack is a first-type cell and a second-type cell that are electrically connected in series, the first-type cell and the second-type cell are cells of different chemical systems, and the first-type cell includes 6 A first cell, the second type of cell includes three second cells, which are arranged in the manner of BAAAAAAAB (A represents the first cell, and B represents the second cell).

"Test methods for cells and battery packs"

1. SOH test method of the first cell and the second cell

Refer to GB/T 31484-2015 "Cycle Life Requirements and Test Methods of Power Batteries for Electric Vehicles" to test the actual capacity of the battery cells, and the ratio of the actual capacity measured by the same test process to the rated capacity of the fresh factory batteries is SOH.

Actual capacity (calculated as: Capx) test steps:

The percentage of Capx to the rated capacity C is the SOH.

2. SOC test method of the first cell and the second cell

3. Test method for the total charging capacity of the negative pole pieces of the first cell and the second cell

(1) The sampling requirements of the pole piece are as follows:

4. Test method for the capacity of the first cell and the second cell:

Select the battery to be tested, use the battery charger and discharge machine and the high and low temperature box to test the standard rate full charge capacity and discharge capacity of the battery at 25°C, and the discharge capacity is the capacity of the battery. Among them, the charging and discharging rate is 0.33C (C represents the rated capacity of the battery cell. Among them, the charging/discharging current is the rate multiplied by the rated capacity of the battery cell, and the rated capacity is based on the battery cell capacity identified in the GBT certification document of the battery cell. ).

Specifically: the test process for the capacity of the cell is as follows: 1) stand at 25°C for 30 minutes; 2) 0.33C constant current discharge to the discharge termination voltage (for example, the NCM chemical system cell is set to 2.8V, the LFP chemical system is set to 2.8V The battery is set to 2.5V), and then let stand for 30 minutes; 3) 0.33C constant current charging to the end-of-charge voltage (for example, the NCM chemical system battery is set to 4.2V, 4.25V, 4.3V according to the specific battery type , 4.35V, 4.4V, 4.45V, etc., the LFP chemical system cell is generally 3.65V, and the charging termination voltage of the cell is recognized as the industry's well-known information), constant voltage charging to the current <0.05C, and then let stand for 5 minutes; 4 )0.33C constant current discharge to discharge termination voltage. At this time, the measured discharge capacity is the capacity value of the cell. For relevant terms and test methods, refer to GB/T 19596, GB/T 31484-2015, GB/T 31485-2015, GB/T 31486-2015 and "Safety Requirements for Power Batteries for Electric Vehicles".

5. Test method for battery pack capacity retention rate:

Refer to GB/T 31484-2015 "Cycle Life Requirements and Test Methods of Power Batteries for Electric Vehicles".

(1) 1000-cycle capacity retention rate (/25℃) test method:

Initial capacity (calculated as: Cap0) test steps:

1) Let the new battery pack stand at 25°C for 30 minutes; 2) 0.33C (C represents the rated capacity of the battery cell. Among them, the charging/discharging current is the rate multiplied by the rated capacity of the battery cell, and the rated capacity is the same as the battery cell's rated capacity. , or the battery module to which the cell belongs or the capacity of the battery cell identified in the GBT certification document of the battery pack to which the cell belongs) Constant current discharge to the discharge termination voltage of the battery pack, and then stand for 30 minutes; 3) 0.33C Charge with constant current to the termination voltage of the battery pack, charge with constant voltage until the current <0.05C, and let stand for 5 minutes; 4) Discharge with constant current at 0.33C to the termination voltage of the battery pack, and then stand for 5 minutes. The discharge capacity measured from step 3) to step 4) is counted as Cap0.

Steps 1) to 4) are one charge-discharge cycle for the battery pack.

Repeat the above steps 1) to 4) 1000 times, the discharge capacity measured at the 1000th time is calculated as Capn, and the capacity retention rate at the 1000th time is: Capn/Cap0*100%.

By the above-mentioned "Cell Preparation" method, the following battery packs of Example 1 and Comparative Example 1 can be obtained. In the battery pack of Example 1 and the battery pack of Comparative Example 1, the negative electrode capacities of the second-type cells (second-type cell capacities) were different from each other.

In addition, by the above-described test method, the following Table 1 showing the comparison results between Example 1 and Comparative Example 1 can be obtained.

According to the above Table 1, in Comparative Example 1, the ratio of the total charge capacity of the first negative electrode piece to the total charge capacity of the second negative electrode piece is 0.78, that is, less than 0.8 (not within the range of 0.8 to 1.2) and other conditions Under exactly the same conditions, the capacity retention rate of the battery pack at the 1000th cycle was significantly lower than that of Examples 1 and 2. In Comparative Example 2, when the ratio of the total charge capacity of the first negative electrode piece to the total charge capacity of the second negative electrode piece is 1.3, that is, exceeds 1.2 (not within the range of 0.8 to 1.2) and other conditions are exactly the same, Compared with Examples 1 and 2, the capacity retention rate of the battery pack at the 1000th cycle also decreased significantly.

It can be seen from this that, compared with the comparative example, by ensuring that the total charging capacity of the negative pole piece of the first battery cell and the second battery cell under the same SOH and SOC state is within a certain range, it can be improved. The capacity retention rate of the 1000th cycle of the battery pack significantly improves the overall cycle life of the battery pack.

In the present application, optionally, the ratio of the compaction density of the first negative pole piece to the compaction density of the second negative pole piece is 0.85 to 1.15. Optionally, the ratio of the compaction density of the first negative pole piece to the compaction density of the second negative pole piece is 0.95 to 1.05. Optionally, both the density of the first negative pole piece and the density of the second negative pole piece are in the range of 1.0 g/cm ³ to 1.9 g/cm ³ . Optionally, both the density of the first negative pole piece and the density of the second negative pole piece are in the range of 1.2 g/cm ³ to 1.8 g/cm ³ .

The inventors of the present application have found through intensive research that: when the compaction density of the negative pole piece is within an appropriate range, the porosity of the negative pole piece is moderate, thereby improving the interface side reaction between the negative pole piece and the electrolyte, inhibiting the The consumption of electrolyte and negative electrode active layer material can effectively improve the cycle life of the battery cell; and since the total volume of pores to be filled in the negative electrode plate is moderate, there is no need to use too much electrolyte, which is conducive to improving the battery core. energy density.

In the present application, by making the compaction density of the first negative pole piece and the compaction density of the second negative pole piece as consistent as possible, the life decay rate of the two types of cells during use can be basically Consistent, can significantly improve the overall life and overall performance of the battery pack.

"Cell Preparation"

Regarding the preparation of the cell, a method similar to the "Preparation of the cell" in the above-mentioned Example 1 was adopted, except that the compaction density was changed to the values shown in the following Examples 3 to 10.

"Test method for compaction density"

The compacted density can be tested using methods known in the art. An exemplary test method for the compaction density of the negative film layer is as follows: take the negative pole piece coated on one side and after cold pressing (if it is a pole piece coated on both sides, the negative film layer on one side can be wiped off first), Punch out a small disc with an area of S1, weigh its weight, and denote it as M1; test the thickness of the negative electrode film layer, denoted as H; then wipe off the negative electrode film layer, and weigh the weight of the negative electrode current collector, denoted as M2; The compaction density of the negative electrode film layer is dc=(M1-M2)/S1/H.

The battery packs of the following Examples 3 to 10 can be obtained by the above-mentioned "Cell Preparation" method. In the battery packs of Examples 3 to 6, the compaction densities of the negative electrode pieces of the first type of cells are the same as each other, but the compaction densities of the negative electrode pieces of the second type of cells are different from each other. In the battery packs of Examples 7 to 10, the ratio of the compaction density of the negative pole pieces of the first type of cells to the compaction density of the negative pole pieces of the second type of cells is the same, but the ratio of the compaction density of the negative pole pieces of the first type of cells The compaction densities of the sheets are different from each other, and the compaction densities of the negative pole sheets of the second type of cells are different from each other.

Moreover, the following Table 2 which shows the comparison result among Examples 3-6 can be obtained by the above-mentioned test method.

According to the above Table 2, the ratio of the compaction density of the first negative pole piece to the compaction density of the second negative pole piece is 0.82 or 1.18, that is, less than 0.85 or greater than 1.15 (not within the range of 0.85 to 1.15) and other When the conditions are exactly the same (Comparative Examples 2 and 3), the capacity retention rate of the battery pack at the 1000th cycle is lower than that of Examples 3 and 4.

It can be seen that, compared with Examples 5 and 6 of the present application, the capacity retention rate of the battery pack at the 1000th cycle can be improved, and the overall life and comprehensive performance of the battery pack can be significantly improved.

In addition, by the above-described test method, the following Table 3 showing the comparison results between Examples 7 to 10 can be obtained.

According to the above Table 3, it can be seen that the compaction density of the first negative pole piece (the compaction density of the second negative pole piece) is 0.95 or 1.95, that is, less than 1 or more than 1.9 (not within the range of 1 to 1.9) and other conditions In exactly the same cases (Examples 9 and 10), the capacity retention rate of the battery pack at the 1000th cycle was lower than that of Examples 7 and 8.

It can be seen that, compared with Examples 9 and 10 of the present application, the capacity retention rate of the battery pack at the 1000th cycle can be improved, and the overall life and comprehensive performance of the battery pack can be further improved.

In the present application, optionally, the ratio of the coating mass per unit area of the negative electrode active material of the first negative electrode pole piece to the coating mass per unit area of the negative electrode active material of the second negative electrode pole piece is 0.85 to 1.15; Optionally, the ratio of the coating mass per unit area of the negative active material of the first negative pole piece to the coating mass per unit area of the negative active material of the second negative pole piece is 0.95 to 1.05; optionally, The coating mass per unit area of the negative active material of the first negative pole piece and the coating mass per unit area of the negative active material of the second negative pole piece are both in the range of 6 mg/cm ² to 17 mg/cm ² ; Optionally, the coating mass per unit area of the negative active material of the first negative pole piece and the coating mass per unit area of the negative active material of the second negative pole piece are both 8 mg/cm ² to 14 mg/cm ² . In the range.

The inventors of the present application have found through intensive research that the coating quality of the active material layer of the negative electrode pole piece needs to be controlled within an appropriate range. The material layer is polarized to improve the power performance of the cell; on the other hand, it can ensure the high energy density of the cell and the module, and reduce the manufacturing cost of the cell per watt-hour.

In the present application, by making the coating mass per unit area of the negative electrode active material of the first negative electrode pole piece as much as possible to be consistent with the coating mass per unit area of the negative electrode active material of the second negative electrode pole piece, it is possible to make the two The life-span decay rate of these batteries is basically the same during use, which can further improve the overall life and comprehensive performance of the battery pack.

"Cell Preparation"

Regarding the preparation of the cells, a method similar to the "Preparation of Cells" in the above-mentioned Example 1 was adopted, except that the coating mass per unit area of the negative electrode active material was changed to the values shown in the following Examples 11 to 18.

"Test method for coating quality per unit area of negative electrode active material"

Take the pole piece that has been coated on one side and has been cold-pressed (if it is a pole piece coated on both sides, you can wipe off the active material layer on one side first), punch it into small discs with an area of S1, and cut them into small discs. Carry out weighing, and its mass is denoted as M1; Then the active material layer on the surface of the above-mentioned pole piece is soaked in a solvent, so that the negative electrode active material layer and the negative electrode current collector are completely peeled off, and the quality of the negative electrode current collector is weighed and denoted as M2; Thus, The coating mass per unit area of the negative pole piece can be calculated according to the formula: coating mass per unit area of the negative pole piece=(M1-M2)/S1.

The battery packs of the following Examples 11 to 18 can be obtained by the above-mentioned "Cell Preparation" method. In the battery packs of Examples 11 to 14, the coating mass per unit area of the negative active material of the negative electrode sheet of the first type of cell is the same, but the coating mass per unit area of the negative active material of the negative electrode sheet of the second type of cell is the same. The qualities are different from each other. In the battery packs of Examples 15 to 18, the difference between the coating mass per unit area of the negative electrode active material of the negative electrode sheet of the first type of cell and the coating mass per unit area of the negative electrode active material of the negative electrode sheet of the second type of cell. The ratios are the same, but the coating mass per unit area of the negative electrode active material of the negative electrode sheet of the first type of cell is different from each other, and the coating mass per unit area of the negative electrode active material of the negative electrode sheet of the second type of cell is different from each other.

In addition, the following Table 4 showing the comparison results between Examples 11 to 14 can be obtained by the above-described test method.

According to the above Table 4, the ratio of the coating mass per unit area of the negative active material of the first negative electrode sheet to the coating mass per unit area of the negative active material of the second negative electrode sheet is 0.83 or 1.18, that is, less than 0.85 or greater than 1.15 (outside the range of 0.85 to 1.15) and other conditions are exactly the same (Examples 13 and 14), the capacity retention rate of the battery pack at the 1000th cycle is lower than that of Examples 11 and 12.

It can be seen from this that, compared with Examples 13 and 14, Embodiments 11 and 12 of the present application can improve the capacity retention rate of the battery pack at the 1000th cycle, and can significantly improve the overall life and comprehensive performance of the battery pack.

Further, by the above-described test method, the following Table 5 showing the results of comparison between Examples 15 to 18 can be obtained.

According to the above Table 5, the coating mass per unit area of the negative active material of the first negative electrode sheet (the coating mass per unit area of the negative active material of the second negative electrode sheet) is 5.5 or 17.5, that is, less than 6.0 or greater than 17.0 (Examples 17 and 18) (Examples 17 and 18) (not within the range of 6.0 to 17.0), the capacity retention rate of the battery pack at the 1000th cycle was lower than that of Examples 15 and 16.

It can be seen that, compared with Embodiments 17 and 18, the 1000th cycle capacity retention rate of the battery pack can be improved, and the overall life and comprehensive performance of the battery pack can be further improved.

In addition, in the above-mentioned embodiments and comparative examples, the positive pole pieces of the first type of cells are all LiFePO ₄ , but the positive pole pieces of the first type of cells can also be made of other materials, such as LiMn _0.5 Fe _0.5 PO ₄ , LiMn _0.6 Fe _0.4 PO ₄ , LiMn _0.7 Fe _0.3 PO ₄ , Na ₃ V ₂ (PO ₄ ) ₂ O ₂ F, LiFe _0.998 Ti _0.002 PO ₄ , LiFe _0.995 Ti _0.005 PO ₄ .

Below, Table 6 shows Examples 19 to 25 when the positive electrode pieces of the first-type battery cells or the second-type battery cells are made of different materials.

According to the above table 6, after doping and coating and optimizing the design of Example 23 (the positive pole piece of the first type of cell is LiFe _0.998 Ti _0.002 PO ₄ and the positive pole piece of the second type of cell is LiNi _0.65 Co _0.079 Mn _0.27 Zr _0.001O2 ), Example 24 (the positive pole piece of the first type of cell is LiFe _0.995 Ti _0.005 PO ₄ and the positive pole piece of the second type of cell is LiNi _0.70 Co _0.065 Mn _0.24 Ti _0.003 W _{0.002 O2} ), the 1000th cycle capacity retention rate of the module is 96% and 98% respectively, showing the most excellent cycle life.

The embodiments or implementations in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments may be referred to each other.

In the description of this specification, reference to the terms "one embodiment," "some embodiments," "exemplary embodiment," "example," "specific example," or "some examples", etc., is meant to incorporate the embodiments A particular feature, structure, material, or characteristic described or exemplified is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features thereof can be equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present application. scope.

Claims

A battery pack comprising at least a first type of battery cell and a second type of battery cell connected in series, wherein the first type of battery cell and the second type of battery cell are cells of different chemical systems,

The first type of battery cell includes N first battery cells,

The second type of battery cell includes M second battery cells, and N and M are positive integers;

When the state of health SOH of the first cell is the same as the SOH of the second cell, and the state of charge SOC of the first cell is the same as the SOC of the second cell, the The ratio of the total charging capacity of the first negative pole piece of the first battery cell to the total charging capacity of the second negative pole piece of the second battery cell is 0.8 to 1.2.
The battery pack of claim 1, wherein,

When the state of health SOH of the first cell is the same as the SOH of the second cell, and the state of charge SOC of the first cell is the same as the SOC of the second cell, the The ratio of the total charging capacity of the first negative pole piece to the total charging capacity of the second negative pole piece is 0.9 to 1.1.
The battery pack of claim 1 or 2, wherein,

The ratio of the discharge capacity of the first negative pole piece to the discharge capacity of the second negative pole piece is 0.8 to 1.2, optionally 0.9 to 1.1.
The battery pack according to any one of claims 1-3, wherein,

The ratio of the rated capacity of the cells of the first type to the rated capacity of the cells of the second type is 0.8 to 1.2, optionally 0.9 to 1.1.
The battery pack according to any one of claims 1-4, wherein the first negative pole piece and the second negative pole piece further satisfy at least one of the following conditions:

(1) The ratio of the compaction density of the first negative pole piece to the compaction density of the second negative pole piece is 0.85 to 1.15, optionally 0.95 to 1.05;

(2) the ratio of the coating mass per unit area of the first negative pole piece to the coating mass per unit area of the second negative pole piece is 0.85 to 1.15, optionally 0.95 to 1.05;

(3) The ratio of the porosity of the first negative pole piece to the porosity of the second negative pole piece is 0.8 to 1.25, optionally 0.9 to 1.1.
The battery pack of any one of claims 1-5, wherein,

The density of the first negative pole piece and the density of the second negative pole piece are each independently 1.0 g/cm 3 to 1.9 g/cm 3 , optionally 1.2 g/cm 3 to 1.8 g/cm 3 .
The battery pack of any one of claims 1-6, wherein,

The coating mass per unit area of the first negative pole piece and the coating mass per unit area of the second negative pole piece are each independently 6 mg/cm 2 to 17 mg/cm 2 , optionally 8 mg/cm 2 to 14 mg/cm 2 .
The battery pack of any one of claims 1-7, wherein,

The porosity of the first negative pole piece and the porosity of the second negative pole piece are each independently 15% to 35%, optionally 20% to 30%.
The battery pack of any one of claims 1-8, wherein,

The negative active material of the first negative pole piece and the negative active material of the second negative pole piece can be independently selected from artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, titanic acid One or more of lithium;

Optionally, the negative active material of the first negative electrode and the negative active material of the second negative electrode have the same composition.
The battery pack of any one of claims 1-9, wherein,

The ratio of the number of cells of the first type to the number of cells of the second type is 0.1 to 50, optionally 2 to 10.
A battery pack comprising the battery pack of any one of claims 1-10.
An electrical device, comprising the battery pack according to any one of claims 1-10 or the battery pack according to claim 11, and using the battery pack or the battery pack as a power source of the electrical device Or energy storage units.
A method of manufacturing a battery pack, comprising the steps of:

Obtain a first-type battery cell and a second-type battery cell, where the first-type battery cell and the second-type battery cell are batteries of different chemical systems,

The first type of battery cell includes N first battery cells,

The second type of battery cell includes M second battery cells, and N and M are positive integers;

In the case where the state of health SOH of the first cell is the same as the SOH of the second cell, and the state of charge SOC of the first cell is the same as the SOC of the second cell, the The ratio of the total charging capacity of the first negative pole piece of the first battery cell to the total charging capacity of the second negative pole piece of the second battery cell is 0.8 to 1.2;

The cells of the first type and the cells of the second type are electrically connected, including in series, to form the battery pack of any one of claims 1 to 10 .
A manufacturing equipment for a battery pack, comprising:

a clamping arm unit, the clamping arm unit is used to obtain the first type of batteries and the second type of batteries, the first type of batteries and the second type of batteries are batteries of different chemical systems,

The first type of battery cell includes N first battery cells,

The second type of battery cell includes M second battery cells, and N and M are positive integers;

In the case where the state of health SOH of the first cell is the same as the SOH of the second cell, and the state of charge SOC of the first cell is the same as the SOC of the second cell, the The ratio of the total charging capacity of the first negative pole piece of the first battery cell to the total charging capacity of the second negative pole piece of the second battery cell is 0.8 to 1.2;

an assembling unit for electrically connecting the first type of battery cell and the second type of battery cell in a manner including a series connection, so as to form the battery pack according to any one of claims 1-10; as well as

a control unit, the control unit is used for controlling the clamping arm unit and the assembling unit.